8 Things All Men Need to Know About a Woman's Period

You probably learned the basics back in middle school health class: Every month, a woman bleeds. This is her period, and it means she isn’t pregnant.

But like everything else you’ve gathered about women since you were a teenager, it’s not quite that simple.

Even though you’ll never have to go through menstruation, it pays to know what actually goes on down there. Follow this guide and see what we mean.

1. It’s more than just blood.

Women will roll their eyes when they read this, but we’re amazed at how many guys don’t actually know what menstruation entails. If you do, go ahead and skip to the next section.

If not, here’s the gist: Every month, her endometrium, or the lining of her uterus, sheds. During the course of her menstrual cycle, this lining plumps up to prepare to nourish a fertilized egg.

If that doesn’t occur, her body doesn’t need the extra tissue. It then gets released during her period, which generally lasts between 2 to 7 days.

2. Timing sex can boost your odds of a baby.

Quick refresher in biology: In order to become pregnant, a woman’s egg must meet your sperm. That can only happen during ovulation, when the egg breaks free from her ovaries.

Exactly when a woman ovulates depends on the length of her cycle, or the number of days between periods. If she has an average 28-day cycle, she’ll usually ovulate around day 14. (Women can use over-the-counter ovulation tests to help them determine when it’s happening.)

But eggs can stay alive for up to 48 hours after ovulation, and sperm for up to 72 hours after ejaculation, says Dr Linda Bradley, director of the Fibroid and Menstrual Disorders Centre at the Cleveland Clinic.

So if she ovulates on day 14, she can still get pregnant from sex on day 11 or day 16.

3. She can get pregnant on her period.

Ever hear that it’s safe to have unprotected sex while she’s bleeding? That’s actually a myth, since not all women have regular cycles, says Dr Nathaniel DeNicola, an obstetrician and gynaecologist at Penn Medicine.

A woman with a short cycle, for instance, could end up ovulating shortly after she stops bleeding. So if you have sex on the last day of her period, it’s possible your sperm could stick around long enough until her egg is released. Which, of course, could lead to pregnancy.

Plus, if her cycles are erratic, she may confuse the start of her period with the light spotting that can occur during ovulation. And if you have unprotected sex during that window, well, that's prime baby-making time.

Bottom line: If you don’t want to be a dad, use some form of birth control every time you have sex, whether she’s on her period or not.

4. She can get a “period” and still be pregnant.

If the condom broke while you were getting busy, you’d probably white-knuckle it every day until she reported her period. But that might not mean relief, since she can actually bleed and still be pregnant.

“It’s not possible to have a real period, where she’s shedding the uterine lining, and a viable pregnancy at the same time” says Dr. DeNicola. “But it’s definitely possible to see spotting, which may look like a period, during a regular pregnancy.”

According to a 2012 study from China, 24 per cent of women reported bleeding during their first trimester, or first 3 months, of pregnancy. This could just be due to the fertilised egg implanting in the uterus or hormonal changes related to pregnancy.

But it can also signal something serious, like problems with the placenta, or a possible miscarriage, says Dr. DeNicola.

5. Cramps suck just as much as she says they do.

An Italian study found that over 80 percent of young women reported pain with their periods. And for about 1 in 3 of them, the pain was so bad that it made them miss out on social events or other obligations.

When her period begins, her levels of a chemical called prostaglandin increase, says Dr. Bradley. This helps her uterus contract in order to expel its lining.

But it also causes cramping – which can feel like throbbing or a dull, constant ache – that can radiate from her lower abdomen to her back and thighs. It can also spark gastrointestinal complaints like diarrhoea.

6. PMS really exists.

If she gets testy with you, resist the urge to make a PMS joke. Premenstrual syndrome occurs during the week or so before her period begins, and it really can make her feel like total crap.

Scientists don’t know what exactly causes PMS, but it seems to be linked to fluctuating levels of the hormones estrogen and progesterone.

Some women may be more sensitive to these changes, says Dr. DeNicola. As a result, they may experience some of the symptoms typically associated with PMS: fatigue, mood swings, food cravings, breast tenderness, cramps, aches, and increased anxiety.

PMS is different from premenstrual dysphoric disorder (PMDD), a less common condition that’s kind of like PMS on steroids.

Women with PMDD can experience severe feelings of depression, inability to concentrate, or changes in sleep patterns that can really hinder their lives. If she’s feeling these symptoms, she should talk to her doctor.

7. Ovulation can rev her up.

According to a Canadian study, women experience more sexual fantasies when they’re ovulating than they do during any other part of their cycle – and they report feeling more turned on by them.

That’s because during that time, her brain sends signals to stimulate her ovaries to get them ready to release the egg. Her levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) spike highest at that point.

These hormonal changes can allow her to become aroused more easily, says Dr Brett Worly, an assistant professor of obstetrics and gynecology at the Ohio State University.

8. Her period might kill her mood – or make her hornier.

When her period begins, levels of the hormones estrogen and progesterone – which are linked to PMS symptoms like moodiness, irritability, and breast tenderness – plummet. As a result, women usually start to feel their mood improve, says Dr. Worly.

But that doesn’t mean she’s ready to slide between the sheets: Cramps can make sex seem unappealing, as can the social stigma of getting it on while bleeding. She may assume you’d be uncomfortable with it, or it may be something she’s self-conscious about.

But some women actually find their arousal increases during their period. “Her pelvic organs can be more sensitive due to the increased blood flow at that time,” Dr. Worly says.